Normally I end up cleaning my lenses in the field and I have found the best and most cost effective solution is as follows.

First of all blow fiercly on the glass to remove larger particles, then take a deep breath and breath on the glass, make sure it looks nice and foggy. Shake your t-shirt to ensure it is free from sand and dirt, think about using a sleeve if too dirty. Make small circular motions over the glass; repeat for persistant marks.

Still no one answered my question lol. Is it safe to clean the lens and LCD screen with alcohol wipe ?

alcohol should be used sparingly. On glass it should be fine, although I am not sure how the coatings react over long term use. On plastic, alcohol can leach things or alter the plastic, depending on the plastic. Perspex becomes turbid after long term use. Given that one does not know how the plastic of the lens or the body reacts, it's probably better to avoid it. Also, the LCD screen, I am not sure if that is actually glass or plastic.I have a screen protector on my LCD, so just wipe it with a cloth (and some breath) if necessary.For the lens elements, first rocket blower to remove dust as much as possible. You don't want to wipe the lens when scratchy dust particles are on it. A brush can help release particles. Only then I use microfiber cloth or clean cotton cloth to wipe, again with some breath if necessary. If there are some persistent grease spots, only then some lens cleaning fluid.

Still no one answered my question lol. Is it safe to clean the lens and LCD screen with alcohol wipe ?

alcohol should be used sparingly. On glass it should be fine, although I am not sure how the coatings react over long term use. On plastic, alcohol can leach things or alter the plastic, depending on the plastic. Perspex becomes turbid after long term use. Given that one does not know how the plastic of the lens or the body reacts, it's probably better to avoid it. Also, the LCD screen, I am not sure if that is actually glass or plastic.I have a screen protector on my LCD, so just wipe it with a cloth (and some breath) if necessary.For the lens elements, first rocket blower to remove dust as much as possible. You don't want to wipe the lens when scratchy dust particles are on it. A brush can help release particles. Only then I use microfiber cloth or clean cotton cloth to wipe, again with some breath if necessary. If there are some persistent grease spots, only then some lens cleaning fluid.

+1. Taught to do it this way on a Short Digital Photography Course by a Professional.Not needed Alcohol yet. Well not for the Lenses anyway.

Beware. A guy I knew in the military was told to clean his tape heads with Alcohol,he tried it with Beer! Go figure.........

Drink a little too much ethyl alcohol, and you might see Ethel. But drink too much methyl alcohol, and you won't see much of anything. The liver enzyme that converts ethanol to a 2-carbon aldehyde (acetaldehyde, which is one of the contributing factors for a hangover) also converts methanol to it's corresponding 1-carbon aldehyde - formaldehyde. Among other effects, the formaldehyde crosslinks the visual pigments in the retina, resulting in blindness.

Still no one answered my question lol. Is it safe to clean the lens and LCD screen with alcohol wipe ?

Yes it is, though i would avoid stronger solvents without checking. Ethanol is fine....

Most cleaning products are isopropanol.

Yes, it should be safe for the lenses.

For the display? Probably. If this were a thin-skinned LCD panel like you'd see on a laptop, I would try to avoid using alcohol too often, and possibly even dilute it 50/50 with water, but for the hard plastic cover on a camera, I wouldn't expect it to hurt anything at all. That said, unless you're shooting in a dusty environment, you're probably better off just wiping the back of the camera on your jeans. It's not like you have to perfectly remove every last trace of fingerprint smudge on the panel.

The downside is that it doesn't clean the lens. It can be used to remove certain things, but for me it has never cleaned anything that doesn't come of with a plain microfiber cloth. After cleaning a lens I tend to wipe it with isopropanol as the last step.

When I bought my 600D/T3i camera with 18-55mm lens, the seller used alcohol wipe and glasses microfiber cleaning cloth to clean both the LCD screen and camera lens. Is that safe ? Or should he have used something else ? Also, I didn't clean my lenses ever since I bought my camera, how often should I clean it and with what ?

spit and sandpaper is the best

but barring that, a chamois or micro-fiber cloth works great and a few drops of FormulaMC or the like if needed. Oh and first use one of those manual puff blower bulbs to try to blow off any sand or grit before rubbing that all over the lens surface